Pillar of Sacrifice

The Pillar of Sacrifice appears at the base of the Sacellum of Boethiah and is a major part in the Boethiah's Calling quest. Getting a non-essential follower to use it will pull them in - it seems to have magnetic properties.

Stabbing a follower with the Blade of Sacrifice while they are pulled in by the pillar will always result in a kill. When a follower is pulled in, a blue dome appears around them. It seems to be bugged, however, as when a weapon is sheathed or unsheathed, the follower will stand normally and sheathe or unsheathe their weapon as if they were not affected by the pillar at all.

The Daedric script around the Pillar of Sacrifice is mirrored, but reads from edge to center: "I am alive because that one is dead. I exist because I have the will to do so." That is a quote from the book "Boethiah's Proving."

The Ebony Blade can be used instead of the Blade of Sacrifice, gaining a charge on it.

It's possible to tell a companion/follower to use the pillar again after the completion of the quest BUT the only way to remove them is by killing them and Boethiah does not appear again using the follower as a conduit, leaving the Dragonborn with one less follower and disappointment.